1. Field of the Invention
The present invention relates to a vehicle navigation apparatus which is capable of executing voice and/or screen display guidance for navigating a vehicle to a destination point as the vehicle is driven.
2. Description of the Prior Art
A conventional vehicle navigation apparatus, for example, disclosed in Laid-open Japanese Patent Application No. SHO 60-202307, is operated in such a manner that, when it is detected that the vehicle has reached a designated specific area in an intersection, the navigation apparatus notifies the correct direction in which the vehicle should next proceed after passing this intersection, by means of voice and/or display guidance. Another conventional vehicle navigation apparatus, for example, disclosed in Laid-open Japanese Patent Application No. SHO 63-21199, provides voice guidance after the vehicle has run a predetermined distance past an intersection.
However, in these conventional navigation systems, the navigation guidance is issued punctually in accordance with a predetermined procedure, along a predetermined route, without regard for whether or not the driver wants such information. Accordingly, these conventional systems are limited in that the navigation guidance is not always provided when the driver wants For example, where navigation guidance is only given concerning an immediate next--approaching intersection, until the vehicle has completely passed that one intersection, the driver cannot obtain information for the intersection succeeding this immediate next--approaching intersection, or a target, before the vehicle passes that one intersection. Therefore, it was difficult to obtain oncoming information sufficiently beforehand to ensure driving safety.
Furthermore, as the navigation guidance is automatically provided every time the vehicle has run a predetermined distance or every time a predetermined time has elapsed, the driver may come to regard such information as a nuisance because the driver hears it even when he does not want it.
Thus, the conventional navigation apparatus is characterized in that it gives the driver navigation information without taking into account the driver's desire or lack of desire for such information. Therefore, there was the inconvenience that the navigation information was not obtained timely, even if the driver wanted to know it.
Furthermore, as numerous data such as that for maps, voice responses and so on is concentrated and stored in the same CDROM it takes a long time to access the required data. Especially, in the case where two successive items of guidance information are issued during a limited time over a short vehicle travel distance, the vehicle may proceed a significant distance while the necessary data is accessed in the massive CDROM and therefore the navigation guidance may not be given to the driver until the vehicle has reached the immediate area before the next target point. Thus, the driver may be forced to suddenly brake or steer the vehicle to change the course in accordance with the given guidance information, endangering driving safety.
That is, the conventional navigation apparatus is disadvantageous in that the required information is not always given to a driver when or where he really wants to know it.